Warm-up system for exhaust system of internal combustion engine

A warm-up system for an exhaust system of an internal combustion engine comprising:

• an electronic control unit configured to perform a warm-up control for warming up an exhaust system component provided in an exhaust passage of the internal combustion engine upon start-up of the internal combustion engine, said electronic control unit further configured to perform failure diagnosis for said exhaust system component after completion of warm-up of said exhaust system component,
• wherein if an operation of the internal combustion engine is repeatedly stopped before completion of the failure diagnosis for a predetermined period of time, then said electronic control unit changes the warm-up control that is performed upon start-up of the internal combustion engine to a control that raises a temperature of said exhaust system component more quickly than the warm-up control performed during said predetermined period.